This article describes the main results of a joint Institut Français du Pétrole (IFP)-Société Nationale Elf Aquitaine (Production) (SNEA) (P) research project on the influence of tectonic stresses on thé petrophysical matrix properties of limestone reservoirs. Research mainly concentrated on the Burdigalien from the Alpilles mountains in ihe Provence région and accessorily on the Turonian from Mareuil in the Aquitaine region and Scaglia Bianca from Monte Conero in Anconia, Italy. The following findings were made: - considerable variations in porosity and permeability can be found, depending on the structural position of the material and, on a smaller scale, on the curve of the loyers; - there is a double porosity and permeability réduction process, either by mechanical settling or by thé crystallization in thé pores of a calcite probably coming from a dissolution occurring along stylolitic joints of tectonic origin. It is also shown that in some specific zones (in periclines or directly underneath deep accidents in thé form of thrust faults) thé effects of tectonic stresses on matrix qualities may be very great and may occur prior to the folding structuration of the loyers.